Osama Bin Laden's videotaped message to America and its allies - his first appearance since the 11 September attacks - is being seen as a cleverly timed shot in the propaganda war.

In the video, broadcast by the Qatari al-Jazeera satellite television station, Bin Laden addresses Americans directly with a chilling threat of more devastating attacks.

Pointing his finger at the camera, Bin Laden said the US had been "struck by God almighty in one of its vital organs, so that its greatest buildings are destroyed".

Bin Laden told Americans they could never feel safe

He also referred to "the infidel's armies [in] the land of Mohammed" - a reference to the US military presence in Saudi Arabia.

Many observers say his message was aimed at the Muslim world, underlining his argument that he is a defender of Islam.

The US has countered by dismissing his comments and dropping huge numbers of leaflets on Afghanistan, stressing that the "terrorists" are the target of the air strikes and not the Afghan people.

Thinking ahead

The BBC's diplomatic correspondent, Barnaby Mason, says the battle now joined is as much one of ideas as of missiles, and both sides realise the importance of the propaganda war.

"American and British leaders have issued carefully prepared political messages," he says.

The prime minister rejected Bin Laden's claims of a "war on Islam"

"The targets were military or terrorist. The campaign was not directed against Muslims or ordinary Afghans - and to prove it, food and medicine were being dropped as well.

"But Osama Bin Laden too had been thinking ahead. It is one of his talents. His video, recorded before the air strikes, spread the opposite message - that it was a war against Islam, and George Bush was the head of the infidels."

In an effort to dispel this, British Prime Minister Tony Blair appeared on the al-Jazeera station on Monday to make what his spokesman described as a response to Bin Laden's comments.

"When we listen to the words of Osama Bin Laden, if he has his way, the regimes that he would replace regimes in the Arab world with would be like the Taliban regime in Afghanistan," said the prime minister.

"I don't believe that anybody seriously wants to live under that kind of regime," he added.

Mr Blair was interviewed in London, with his words dubbed into Arabic.

US servicemen make no secret that they have revenge in mind

As the airstrikes continue, civilian casualties could become a powerful propaganda weapon.

"However carefully targeted the air strikes, every civilian casualty will tend to undermine the Western argument that they are not an attack on the Afghan people," says our correspondent.

"On the other hand, minimum casualties combined with clear military success would keep nervous Muslim governments lined up in the coalition against terrorism, however reluctantly, and give less cause for angry demonstrations in the streets."

Central player

The Americans hope, the correspondent notes, that the attacks will "demoralise the Taleban and encourage its opponents".

"The Americans hope this military-psychological campaign will do the work for them and deliver up Osama bin Laden and his network."

Al-Jazeera television which broadcast Osama Bin Laden's message has become a key player in the propaganda battle.

Following Sunday night's raids it carried reports that life was returning to normal in Kabul.

Popular opinion could prove to be a crucial factor

"People are out in the streets, but in relatively fewer numbers than before ... some people looked gloomy," said a correspondent reporting from the city.

Possibly in reaction, British Prime Minister Tony Blair made a decision to speak on the network to explain the reasons for the US-led attacks against Afghanistan.

"He will make absolutely clear that this is a war against terrorism to underline very clearly to the Middle East and the region that this is not a war against Islam," the prime minister's spokesman said.

Inside Afghanistan itself, Taleban radio is saying the attacks have caused no damage or casualties, and have instead boosted morale.